The overall objective of this proposal is to develop a better understanding of the basic mechanisms of action of Photodynamic Therapy (PDT). The program is an integration of research activities at Henry Ford Hospital, Wayne State University and Oakland University and a direct extension of other ongoing research collaborations in the area of PDT. The project consists of two cores and four separate proposals. The cores are to support overall administrative functions and for biostatistical support of all four projects. Project 1 proposes to investigate parameters for the effectiveness of PDT in primary tumors in pet animals. Project 2 plans to investigate the possibility of combining PDT with another new treatment modality, hyperthermia, which has at least one physiological response mechanism in common with PDT. Normal tissue response to PDT, in particular brain, will be studied in Project 3. Finally, Project 4 proposes to compare PDT with conventional illumination to illumination by chemiluminescence. Ultimately, these studies will provide a better understanding of the underlying mechanisms involved in PDT.